Adjust Valgrind macro usage to protect chunk headers

Prior to this commit we only ever protected MemoryChunk's requested_size
field with Valgrind NOACCESS.  This means that if the hdrmask field is
ever accessed accidentally then we're not going to get any warnings from
Valgrind about it.  Valgrind would have warned us about the problem fixed
in 92957ed98 had we already been doing this.

Per suggestion from Tom Lane

Reviewed-by: Richard Guo
Discussion: https://postgr.es/m/1650235.1672694719@sss.pgh.pa.us
Discussion: https://postgr.es/m/CAApHDvr=FZNGbj252Z6M9BSFKoq6BMxgkQ2yEAGUYoo7RquqZg@mail.gmail.com

1 files changed, 29 insertions, 7 deletions

diff --git a/src/backend/utils/mmgr/alignedalloc.c b/src/backend/utils/mmgr/alignedalloc.c
index 9b975739d17..627e988852b 100644
--- a/src/backend/utils/mmgr/alignedalloc.c
+++ b/src/backend/utils/mmgr/alignedalloc.c
@@ -31,6 +31,8 @@ AlignedAllocFree(void *pointer)
 	MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
 	void	   *unaligned;
 
+	VALGRIND_MAKE_MEM_DEFINED(chunk, sizeof(MemoryChunk));
+
 	Assert(!MemoryChunkIsExternal(chunk));
 
 	/* obtain the original (unaligned) allocated pointer */
@@ -58,12 +60,17 @@ void *
 AlignedAllocRealloc(void *pointer, Size size)
 {
 	MemoryChunk *redirchunk = PointerGetMemoryChunk(pointer);
-	Size		alignto = MemoryChunkGetValue(redirchunk);
-	void	   *unaligned = MemoryChunkGetBlock(redirchunk);
+	Size		alignto;
+	void	   *unaligned;
 	MemoryContext ctx;
 	Size		old_size;
 	void	   *newptr;
 
+	VALGRIND_MAKE_MEM_DEFINED(redirchunk, sizeof(MemoryChunk));
+
+	alignto = MemoryChunkGetValue(redirchunk);
+	unaligned = MemoryChunkGetBlock(redirchunk);
+
 	/* sanity check this is a power of 2 value */
 	Assert((alignto & (alignto - 1)) == 0);
 
@@ -110,11 +117,18 @@ AlignedAllocRealloc(void *pointer, Size size)
 MemoryContext
 AlignedAllocGetChunkContext(void *pointer)
 {
-	MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
+	MemoryChunk *redirchunk = PointerGetMemoryChunk(pointer);
+	MemoryContext cxt;
 
-	Assert(!MemoryChunkIsExternal(chunk));
+	VALGRIND_MAKE_MEM_DEFINED(redirchunk, sizeof(MemoryChunk));
 
-	return GetMemoryChunkContext(MemoryChunkGetBlock(chunk));
+	Assert(!MemoryChunkIsExternal(redirchunk));
+
+	cxt = GetMemoryChunkContext(MemoryChunkGetBlock(redirchunk));
+
+	VALGRIND_MAKE_MEM_NOACCESS(redirchunk, sizeof(MemoryChunk));
+
+	return cxt;
 }
 
 /*
@@ -126,7 +140,15 @@ Size
 AlignedAllocGetChunkSpace(void *pointer)
 {
 	MemoryChunk *redirchunk = PointerGetMemoryChunk(pointer);
-	void	   *unaligned = MemoryChunkGetBlock(redirchunk);
+	void	   *unaligned;
+	Size		space;
+
+	VALGRIND_MAKE_MEM_DEFINED(redirchunk, sizeof(MemoryChunk));
+
+	unaligned = MemoryChunkGetBlock(redirchunk);
+	space = GetMemoryChunkSpace(unaligned);
+
+	VALGRIND_MAKE_MEM_NOACCESS(redirchunk, sizeof(MemoryChunk));
 
-	return GetMemoryChunkSpace(unaligned);
+	return space;
 }